WASHINGTON — In his first day at the office as secretary of state on Monday, John Kerry sought to send the message that he had an affinity for the nation’s diplomats and would look after their security.

“Exhilarating to walk into @StateDept today,” Mr. Kerry, who is the son of a diplomat, posted on Twitter. “Dad on mind! JK.”

Speaking to the hundreds of staff members who greeted him in the State Department lobby, Mr. Kerry recalled Ambassador J. Christopher Stevens and the three other Americans who died in the Sept. 11, 2012, attack on the diplomatic compound in Benghazi, Libya.

“Everything I do will be focused on the security and safety of our people,” said Mr. Kerry.

To underscore that point, Mr. Kerry later in the day took a short drive across the Potomac River to visit the State Department’s Bureau of Diplomatic Security in Rosslyn, Va.

In his confirmation hearing on Jan. 24, Mr. Kerry suggested that he planned to make a diplomatic push on Israeli-Palestinian issues, an area that has not received sustained high-level attention by the Obama administration since a failed effort to broker talks between the two sides in 2010.

That has led to speculation that Mr. Kerry’s first overseas trip may be to the Middle East. Even before arriving for work on Monday, he made a round of calls to Israeli and Palestinian leaders.

On Sunday, Mr. Kerry spoke with the Israeli prime minister, Benjamin Netanyahu, whom he praised for releasing frozen tax revenues to the Palestinian Authority, and on Saturday with Israel’s president, Shimon Peres.

He also spoke with Mahmoud Abbas, the president of the Palestinian Authority, and indicated that he would press Congress to provide almost $500 million in assistance to the authority.

A spokesman for Mr. Abbas, Nabil Abu Rudeineh, told reporters that Mr. Kerry had promised to visit the Middle East “to preserve the political path,” though no date for the trip was announced.

In other Sunday calls, Mr. Kerry spoke to the foreign ministers from Japan and South Korea. On Monday, he continued the calls, which have included the foreign ministers of Britain, France, Germany, Turkey, Mexico and Canada. Mr. Kerry, who is an avid user of Twitter, posted a photo of himself on the phone with William Hague, the British foreign secretary.

Much of Mr. Kerry’s day, however, was spent reaching out to the American diplomats he has been eager to lead.

Mr. Kerry has brought his own press adviser to the State Department, Glen Johnson, a former reporter for the Boston Globe who has covered Mr. Kerry and Massachusetts politics for years. But there were also indications that some top-level senior State Department officials who had worked with Hillary Rodham Clinton would stay on.

Mr. Kerry’s effort at outreach extended to members of a youth orchestra from Afghanistan as well. After hearing the orchestra was playing in a State Department auditorium, Mr. Kerry showed up at the event and volunteered that he had played guitar as a teenager in a rock band called the Electras.

During his morning in the State Department lobby, Mr. Kerry reached even further back in his past, brandishing the diplomatic passport that he had been given when he was 11 years old and that he used when his father was assigned to post-World War II Germany. The young Mr. Kerry used to bicycle around Berlin and once used his passport to cross into the Russian sector.

“When my dad learned what I had done he was not enthralled,” Mr. Kerry recalled, prompting a wave of laughter in the audience. “I was told I could’ve been an international incident. He could’ve lost his job. And my passport, this very passport, was promptly yanked, and I was summarily grounded. Anyway, lessons learned.”

Correction:

An earlier version of this article misstated the day on which John Kerry called Shimon Peres, Israel’s president. It was on Saturday, not on Sunday.

A version of this article appears in print on , on Page A10 of the New York edition with the headline: Reporting for Duty, Kerry Pledges to Protect Diplomats. Order Reprints | Today’s Paper | Subscribe